On Oxytricha fallax (Hypotricha, Ciliata): description and analysis of morphogenesis during and immediately following conjugation; use of mutants to delineate the cytogenetic processes and the processes of encystment and excystment; determination and inheritance of variations in the cell cortex. On Paramecium aurelia, syngen 4 (Holotricha, Ciliata): mapping of the detailed structure of the cell cortex through the cell cycle and correlation with timing of nuclear events; analysis of genic and cortical contributions to the determination and interitance of structural variations in the cell cortex; mode of action of mutational blocks to the directed movements of cell organelles; locating mutant genes on chromosomal maps; constructing multiple marker stocks; analysis of mutations showing abnormal genetic behavior; analysis of nuclear differentiation.